Although Jenkins was the Locomotive Superintendent the early years of this period saw Hawkshaw specifying the locomotives.
As Hawkshaw was not a locomotive engineer the resultant locomotives were not of the best and were hopelessly outdated long before they were withdrawn.
Hurst left to join the North British Railway in 1854 and Jenkins continued on his own.

Following the death of Jenkins responsibility passed to Yates as Indoor Superintendent and Hurst returned as the Outdoor Superintendent. Hurst retired in 1875 and Yates resigned.
A disastrous fire at the Miles Platting works in 1873 led to the building of the new Horwich Works.

The official system of numbered classes was not introduced until 1919, therefore
classes are listed here according to the number of the first locomotive built.

The "number only" classes are those introduced by George Hughes in 1919 and shown in the L&YR working timetable appendix of 1921.[17] There is also a series of unofficial "letter and number" classes which was devised by the author R. W. Rush, and which has been copied by some other authors.[18]